1. Field of the Invention
This invention relates to thermoplastic polymer compositions. In one aspect, the invention relates to a polymer composition having improved thermal stability at high temperatures. In a second aspect, the invention relates to a method of improving the thermal stability of a poly(arylene sulfide) resin and articles produced therefrom at high temperatures. In a third aspect, the invention relates to articles having improved thermal stability at high temperatures.
2. Description of the Prior Art
Although poly(phenylene sulfide) ("PPS") resins and articles produced therefrom are well known for their stability, strength and resistance to chemicals, they often have insufficient thermal stability at high temperatures. For example, PPS films and fibers tend to degrade upon extended exposure to temperatures of 150.degree. C. and higher. If the service life of PPS articles such as films and fibers at 150.degree. C. and higher could be extended, the utility of the articles would be greatly expanded.
The thermal and oxidative degradation mechanisms of PPS are very complex and are not completely understood, particularly at temperatures ranging from 150.degree. C. to 300.degree. C. Degradation of PPS resins and articles produced therefrom tends to increase with increasing temperatures. It is known that the thermal stability and other physical properties of certain thermoplastic resins can be improved by the addition of various additives thereto. Unfortunately, there are no additives or additive systems that function to improve the thermal stability and other physical properties of all thermoplastic resins. Due to varying mechanisms of thermal and oxidative degradation, the fact that a particular additive or additive system improves certain physical properties of one type of thermoplastic resin does not necessarily make it probable or even likely that the same additive or additive system will improve the same or other physical properties of a different thermoplastic resin. Similarly, the fact that a particular additive or additive system is known to function in a certain way in one resin does not make it probable or even likely that the same additive or additive system will function in different ways in the same or other resins.
By the present invention, it has been discovered that the high temperature thermal stability of PPS resins and articles produced therefrom is greatly improved by adding certain thermal stabilizers thereto.